CA2184022C - Thin-film multilayered electrodes and method of fabricating same - Google Patents
Thin-film multilayered electrodes and method of fabricating sameInfo
- Publication number
- CA2184022C CA2184022C CA002184022A CA2184022A CA2184022C CA 2184022 C CA2184022 C CA 2184022C CA 002184022 A CA002184022 A CA 002184022A CA 2184022 A CA2184022 A CA 2184022A CA 2184022 C CA2184022 C CA 2184022C
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- Prior art keywords
- thin
- film
- dielectric
- conductors
- thin films
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P7/00—Resonators of the waveguide type
- H01P7/08—Strip line resonators
- H01P7/082—Microstripline resonators
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/20—Frequency-selective devices, e.g. filters
- H01P1/201—Filters for transverse electromagnetic waves
- H01P1/203—Strip line filters
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P3/00—Waveguides; Transmission lines of the waveguide type
- H01P3/02—Waveguides; Transmission lines of the waveguide type with two longitudinal conductors
- H01P3/08—Microstrips; Strip lines
- H01P3/081—Microstriplines
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P3/00—Waveguides; Transmission lines of the waveguide type
- H01P3/18—Waveguides; Transmission lines of the waveguide type built-up from several layers to increase operating surface, i.e. alternately conductive and dielectric layers
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/0213—Electrical arrangements not otherwise provided for
- H05K1/0237—High frequency adaptations
Abstract
A thin-film multilayered electrode of a high frequency electromagnetic field coupled type is disclosed. The thin-film multilayered electrode comprises thin-film conductors and dielectric thin films alternately stacked on a dielectric substrate so that a plurality of TEM mode transmission lines are multilayered. A film thickness of each of the dielectric thin films isset so that phase velocities of TEM waves which propagate through at least two of the plurality of TEM mode transmission lines are made substantially equal to each other, and a film thickness of each of the thin-film conductors isset so as to be smaller than a skin depth of a frequency which is used so that electromagnetic fields of at least two of the plurality of TEM mode transmission lines are coupled with each other. The thin-film conductors include at least one adhesive layer having a large adhesion strength at one or more of interfaces between the dielectric substrate and the thin-film conductor and the interfaces between the thin film conductors and the dielectric thin films.
Description
21840~2 THIN-FILM MULTILAYERED ELECTRODE
AND METHOD OF FABRICATING SAME
The present invention relates to a thin-film electrode and, more particularly, to thin-film multilayered electrodes used in RF (radio frequency) tr~n.~mi.~sion lines, RF resonators, RF filters, and so on and also to a method of fabricating the thin-film multilayered electrodes.
A high frequency electrom~gn~tic field coupled type thin-film multilayered electrode (hereinafter simply referred to as the "thin-film multilayered electrode") is disclosed in the TntPrn~tional Publication No. WO
95/06336 which was filed on March 7, 1994 as the International Patent Application No. PCT/JP94/00357 and is ~ ign~cl to Murata Manufacturing Co., Ltd.
Specifically, as shown in Fig. 1, a thin-film multilayered electrode 101 includes thin-film conductors 121 to 125 and thin-film dielectrics 131 to 134 alternately stacked on a dielectric substrate 110. The pairs of thin film conductors 121 and 122, 122 and 123, 123 and 124, and 124 and 125 and the thin film dielectrics 131 to 134 sandwiched therebetween constitute a plurality of TEM mode tr~n~mi~ion lines L2 to L5, respectively.
The thin-film multilayered electrode 101 con~titntes a micro-strip line in 2 o cooperation with a ground conductor 111 formed on the bottom surface of the dielectric substrate 110.
Based on the number of layers of the thin-film conductors 121 to 125 and the thin-film dielectrics 131 to 134, a film thickness of each of thethin-film dielectrics 131 to 134 is set so that phase velocities of TEM waves which propagate through at least two of the plurality of TEM mode tr~n~mi~ion lines L2 to L5 are made subst~nti~lly equal to each other.
Moreover, based on the number of layers of the thin-film conductors 121 to 125 and the thin-film dielectrics 131 to 134, a film thickn~ss of each of the thin-film conductors 121 to 125 is set so as to be smaller than a skin depth of a frequency which is intended to be used, so that electrom~gn~tic fields of at least two of the plurality of TEM mode tr~n~mi~.cion lines L2 to L5 are coupled with each other.
In the thin-film multilayered electrode 101, when the TEM
mode trAn~mi~ion lines L2 to LS are excited by a high frequency signal, each of the thin-film conductors 121 to 125 tr~n~mits a part of the high frequency power incident thereon via an adjacent thin-film dielectric to a thin-film 5 conductor adjacent in a dirrer~ direction, while reflecting a part of the highfrequency power into the adjacent thin-film conductor via the thin-film dielectric. Within the thin-film dielectrics 131 to 134 each of which is sandwiched by two adjacent thin-film conductors 121 and 122, 122 and 123, 123 and 124, and 124 and 125, the reflection wave and tr~n.~mi~ion wave resonate, while two oppositely directed high frequency ~;u-.c -l~ flow in the vicinity of the upper and lower surfaces of the thin-films conductors 121 to 125. Therefore, since the film thickness of each of the thin-film conductors 121 to 125 is smaller than the skin depth, the two oppositely directed high frequency cullcnls h~lelrelt; with each other, and are canceled by each other except for a lc~ ining part thereof. In this way, in the thin-film multilayered electrode 101, a resonance energy or a tr~n.~mi~sion energy in adjacent thin-film rlielectrics 131 to 134 is coupled with each other via the thin-film conductors 121 to 125. On the other hand, the thin-film dielectrics 131 to 134 have a displacement current generated by an electromagnetic field, which 2 o causes a high frequency current to be generated at the surface of their adjacent thin-film conductors 121 to 125.
Furthermore, since phase velocities of TLM mode waves which propagate through at least two of the plurality of TEM mode tr~n~mi.c~ion lines L2 to LS are made subst~nti~lly equal to one another, high frequency currents flowing through the thin film conductors 121 to 125 are subst~nti~lly in phase with each other. As a result of this, the high frequency ~;ulre-ll~
flowing in the thin-film conductors 121 to 125 in phase increase the effective skin depth. Therefore, when excitation is effected by a high frequency signal, an electromagnetic energy of the high frequency signal is transferred to an 3 o adjacent tr~n.cmi.~sion line through an electrom~gn~tic coupling of the adjacent TEM mode tr~n~mi~sion lines L2 to LS whose electromagnetic fields are 2t 84022 coupled, while the electrom~gnPtic energy propagates in the longitu-lin~l direction of the tr~ncmic~ion lines L2 to LS. In this case, the electrom~n~tic energy of high frequency propagates in the longitu-lin~l direction of the lines through the electri~lly coupled tr~n~mi~ion lines L2 to LS. Thus, the skin depth is effectively increased and conductor loss and the surface resistance canbe reduced, with remarkably reduced external dimensions.
Thus, use of the thin-film multilayered electrode makes it possible to offer high frequency tr~n~mi~inn lines with smaller tr~n~mi~ion loss, high frequency resonators or high frequency filters having an extremely o large no-loaded Q, or high frequency devices having small size and weight.
In the thin-film multilayered electrode 101, the thin-film conductors are made of a single material of a high conductivity such as Cu or Ag. However, Cu and Ag used for the conductive thin films have the following problems, which are caused by the fact that they wealdy adhere to oxides forming the dielectric thin films and dielectric substrate:
(1) During fabrication of the thin-film multilayered electrode, the films may peel off.
(2) After fabrication of the thin-film multilayered electrode, ~nvi~on-llental conditions are varied repeatedly, whereby stress is accumulated 2 o in the electrode. As a result, the films may peel off.
(3) Stress is accum~ ted in the electrode because of thermal distribution created during the use of the electrode and because a temperature dirre~ ce is created between a time when the electrode is used and a time when it is not used. As a result, the films may peel off.
It is therefore an object of the invention to solve the foregoing problems and provide a highly reliable thin-film multilayered electrode in which conductive thin films are adhered strongly in intim~te contact with a dielectric substrate or with (li~l~ctric thin films. It is another object of theinvention to provide a method of fabricating the thin-film multilayered 3 0 electrode.
AND METHOD OF FABRICATING SAME
The present invention relates to a thin-film electrode and, more particularly, to thin-film multilayered electrodes used in RF (radio frequency) tr~n.~mi.~sion lines, RF resonators, RF filters, and so on and also to a method of fabricating the thin-film multilayered electrodes.
A high frequency electrom~gn~tic field coupled type thin-film multilayered electrode (hereinafter simply referred to as the "thin-film multilayered electrode") is disclosed in the TntPrn~tional Publication No. WO
95/06336 which was filed on March 7, 1994 as the International Patent Application No. PCT/JP94/00357 and is ~ ign~cl to Murata Manufacturing Co., Ltd.
Specifically, as shown in Fig. 1, a thin-film multilayered electrode 101 includes thin-film conductors 121 to 125 and thin-film dielectrics 131 to 134 alternately stacked on a dielectric substrate 110. The pairs of thin film conductors 121 and 122, 122 and 123, 123 and 124, and 124 and 125 and the thin film dielectrics 131 to 134 sandwiched therebetween constitute a plurality of TEM mode tr~n~mi~ion lines L2 to L5, respectively.
The thin-film multilayered electrode 101 con~titntes a micro-strip line in 2 o cooperation with a ground conductor 111 formed on the bottom surface of the dielectric substrate 110.
Based on the number of layers of the thin-film conductors 121 to 125 and the thin-film dielectrics 131 to 134, a film thickness of each of thethin-film dielectrics 131 to 134 is set so that phase velocities of TEM waves which propagate through at least two of the plurality of TEM mode tr~n~mi~ion lines L2 to L5 are made subst~nti~lly equal to each other.
Moreover, based on the number of layers of the thin-film conductors 121 to 125 and the thin-film dielectrics 131 to 134, a film thickn~ss of each of the thin-film conductors 121 to 125 is set so as to be smaller than a skin depth of a frequency which is intended to be used, so that electrom~gn~tic fields of at least two of the plurality of TEM mode tr~n~mi~.cion lines L2 to L5 are coupled with each other.
In the thin-film multilayered electrode 101, when the TEM
mode trAn~mi~ion lines L2 to LS are excited by a high frequency signal, each of the thin-film conductors 121 to 125 tr~n~mits a part of the high frequency power incident thereon via an adjacent thin-film dielectric to a thin-film 5 conductor adjacent in a dirrer~ direction, while reflecting a part of the highfrequency power into the adjacent thin-film conductor via the thin-film dielectric. Within the thin-film dielectrics 131 to 134 each of which is sandwiched by two adjacent thin-film conductors 121 and 122, 122 and 123, 123 and 124, and 124 and 125, the reflection wave and tr~n.~mi~ion wave resonate, while two oppositely directed high frequency ~;u-.c -l~ flow in the vicinity of the upper and lower surfaces of the thin-films conductors 121 to 125. Therefore, since the film thickness of each of the thin-film conductors 121 to 125 is smaller than the skin depth, the two oppositely directed high frequency cullcnls h~lelrelt; with each other, and are canceled by each other except for a lc~ ining part thereof. In this way, in the thin-film multilayered electrode 101, a resonance energy or a tr~n.~mi~sion energy in adjacent thin-film rlielectrics 131 to 134 is coupled with each other via the thin-film conductors 121 to 125. On the other hand, the thin-film dielectrics 131 to 134 have a displacement current generated by an electromagnetic field, which 2 o causes a high frequency current to be generated at the surface of their adjacent thin-film conductors 121 to 125.
Furthermore, since phase velocities of TLM mode waves which propagate through at least two of the plurality of TEM mode tr~n~mi.c~ion lines L2 to LS are made subst~nti~lly equal to one another, high frequency currents flowing through the thin film conductors 121 to 125 are subst~nti~lly in phase with each other. As a result of this, the high frequency ~;ulre-ll~
flowing in the thin-film conductors 121 to 125 in phase increase the effective skin depth. Therefore, when excitation is effected by a high frequency signal, an electromagnetic energy of the high frequency signal is transferred to an 3 o adjacent tr~n.cmi.~sion line through an electrom~gn~tic coupling of the adjacent TEM mode tr~n~mi~sion lines L2 to LS whose electromagnetic fields are 2t 84022 coupled, while the electrom~gnPtic energy propagates in the longitu-lin~l direction of the tr~ncmic~ion lines L2 to LS. In this case, the electrom~n~tic energy of high frequency propagates in the longitu-lin~l direction of the lines through the electri~lly coupled tr~n~mi~ion lines L2 to LS. Thus, the skin depth is effectively increased and conductor loss and the surface resistance canbe reduced, with remarkably reduced external dimensions.
Thus, use of the thin-film multilayered electrode makes it possible to offer high frequency tr~n~mi~inn lines with smaller tr~n~mi~ion loss, high frequency resonators or high frequency filters having an extremely o large no-loaded Q, or high frequency devices having small size and weight.
In the thin-film multilayered electrode 101, the thin-film conductors are made of a single material of a high conductivity such as Cu or Ag. However, Cu and Ag used for the conductive thin films have the following problems, which are caused by the fact that they wealdy adhere to oxides forming the dielectric thin films and dielectric substrate:
(1) During fabrication of the thin-film multilayered electrode, the films may peel off.
(2) After fabrication of the thin-film multilayered electrode, ~nvi~on-llental conditions are varied repeatedly, whereby stress is accumulated 2 o in the electrode. As a result, the films may peel off.
(3) Stress is accum~ ted in the electrode because of thermal distribution created during the use of the electrode and because a temperature dirre~ ce is created between a time when the electrode is used and a time when it is not used. As a result, the films may peel off.
It is therefore an object of the invention to solve the foregoing problems and provide a highly reliable thin-film multilayered electrode in which conductive thin films are adhered strongly in intim~te contact with a dielectric substrate or with (li~l~ctric thin films. It is another object of theinvention to provide a method of fabricating the thin-film multilayered 3 0 electrode.
A thin-film multilayered electrodes according to the present invention may comprise thin-film conductors and dielectric thin films ~1tern~tP,ly stacked on a ~ lectric substrate so that a plurality of TEM mode tr~n~mi~ion lines are multilayered. Each pair of the thin-film conductors the dielectric thin film sandwiched therebetween conctitllting a TEM mode tr~n~mi~ion line. Based on a number of multilayered layers of the thin-film conductors and the dielectric thin films, a film thickn~ss of each of the dielectric thin films is set so that phase velocities of TEM waves which propagate through at least two of the plurality of TEM mode t~n~mi~ion o lines are made subst~nti~11y equal to each other. Further, based on the number of multilayered layers of the thin-film conductors and the dielectric thin films, a film thicknPss of each of the thin-film conductors is set so as tobe smaller than a skin depth at a frequency which is to be used, so that electromagnetic fields of at least two of the plurality of TEM mode tr~n~mi~sion lines are coupled with each other. The thin-flm multilayered electrodes further include at least one adhesive layer having a large adhesion strength at one or more of the interfaces between the dielectric substrate and the thin-film conductor, and/or the intPrf~ces between the thin film conductors and the dielectric thin films.
2 o As described above, in the thin-film multilayered electrode according to the invention, an adhesive layer or layers of great adhesion strength are placed in the position of at least one of the above-mentioned interfaces. The strength of adhesion between the successive thin films forming the thin-film multilayered electrode is thereby increased. This can 2 5 enhance the reliability of the electrode.
For the purpose of illustrating the invention, there are shown in the dMwings several forms which are presently p.~re.r~d, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.
3 o Fig. 1 is a perspective view of a conventional thin-film multilayered electrode and micro-strip lines.
2 o As described above, in the thin-film multilayered electrode according to the invention, an adhesive layer or layers of great adhesion strength are placed in the position of at least one of the above-mentioned interfaces. The strength of adhesion between the successive thin films forming the thin-film multilayered electrode is thereby increased. This can 2 5 enhance the reliability of the electrode.
For the purpose of illustrating the invention, there are shown in the dMwings several forms which are presently p.~re.r~d, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.
3 o Fig. 1 is a perspective view of a conventional thin-film multilayered electrode and micro-strip lines.
- 5 ~ 2~84022 Fig. 2 is a tli~grAm showing the relation between the thickness of Ti thin films which can serve as adhesive layers and their adhesion strength.
Fig. 3 is a diagram showing the relation between the thickness of Ti thin films which can serve as adhesive layers and their resistivity.
Fig. 4A is a perspective view showing a circular TM mode resonator equipped with a thin-film multilayered electrode according to a first example of the invention.
Fig. 4B is a partial cross-sectional view of a thin-film conductor lo used in the circular TM mode resonator shown in Fig. 4A.
Figs. SA to SF are views illustrating a method of fabric~ting circular TM mode resonators equipped with thin-film multilayered electrodes according to the first example of the invention.
Fig. 6A is a perspective view of a microstrip line resonator equipped with a thin-film multilayered electrode according to a second example of the invention.
Fig. 6B is a partial cross-sectional view of a thin-film conductor used in the microstrip line resonator shown in Fig. 6A.
Figs. 7A to 7F are views illllstr~ting a method of fabricating 2 0 microstrip line resonators equipped with thin-film multilayered electrodes according to the second example of the invention.
The inventors of the present invention have conducted various experiments and studied abut methods of improving the strength with which the conductive thin films adhere to the dielectric substrate and to the dielectric thin films. It has been discovered that the strength is improved by placing an adhesive layer or layers of Ti or the like at the interface between the conductive thin film and the dielectric substrate or at the interfaces between the conductive thin films and the dielectric thin films.
That is, a thin-film multilayered electrode according to the 3 o present invention comprises a dielectric substrate on which conductive thin films and dielectric thin films are alternately multilayered. This thin-film 2~ 84022 multilayered electrode is characteri7ed in that an adhesive layer having a largeadhesion strength is placed at one or more of the interf~ces between the ~1ie1ectric substrate and the overlying conductive thin film and/or the interfaces between the conductive thin films and the dielectric thin films.
In the thin-film multilayered electrode according to the present invention, the adhesive layer having a large adhesion strength is a layer or thin film which provides larger adhesion strength when placed in the position of at least one of the above-mentioned interfaces, than if the conductive thin films were directly bonded to the dielectric substrate or to the dielectric thin1 o films.
It is preferable that the material of the adhesive layer or layers of the thin-film multilayered electrode be at least one species selected from the group con~i~ting of Ti, Cr, Ni, and alloys co~ inil-g at least one of them.
The adhesive layer has preferably a thickness of more than 20 nm.
A method of fabricating the thin-film multilayered electrode according to the invention is characterized in that the conductive thin films, the adhesive layer or layers, and the dielectric thin films are formed by continuous process steps under a vacuum without breaking the vacuum during the process steps.
2 o For example, where a thin Cu film having a film thickness of 1 ,um was formed as a conductive thin film on a glass substrate, or a dielectric substrate, a thin film of Ti was placed as an adhesive layer at the interface between the glass substrate and the Cu thin film. The relation of the film thickness of the Ti thin film and the adhesion strength obtained in this case isshown in Fig. 2. It can be seen from Fig. 2 that when the film thickness of the Ti thin film was less than about 20 nm, the adhesion strength was insufficient. In addition, a slight change in the film thickn~ ss resulted in a great variation of the adhesion strength. However, it was observed that as long as the thickness was more than about 20 nm, the adhesion strength was 3 0 sufficiently large. Furthermore, the stability was improved since the adhesion strength was subst~nti~11y constant.
A thin-film multilayered electrode was fabricated by alternately l~min~ting conductive thin films (Cu thin films) and dielectric thin films (glass thin films) on a dielectric substrate (glass substrate). An adhesive tape was stuck to the thin-film multilayered electrode and peeled off. Where thin films 5 of Ti having film thicknesses of less than 20 nm were placed at the interface between the dielectric substrate (glass substrate) and the conductive thin film (Cu thin film) and at the interfaces between the conductive thin films (Cu thin films) and the dielectric thin films (glass thin films), peeling of the multilayered films was observed. Where thin films of Ti having film thicknesses of more than 20 nm were placed, no peeling of the multilayered films was observed.
Thin films of Ti having various film thickn~sses were formed on glass substrates by ~u~e~-hlg techniques, and their resistivities were measured. The results are shown in Fig. 3. It can be seen from Fig. 3 that where the film thicknesses of the Ti thin films were less than about 20 nm, the electrical resistivities were rapidly increased and that a slight deviation from the design~l film thickness greatly affects the characteristics of the thin-film multilayered electrode with undesirable results. On the other hand, where the film thickn~sses of the Ti thin films were more than about 20 nm, 2 0 the resistivities were low. In addition, the stability was enhanced since the resistivity did not vary greatly with the thickness. Hence, a slight deviation from the design~d film thickness does not greatly affect the characteristics. Itcan be seen that this structure can be advantageously applied to an RF
electrom~gnt tic~lly coupled thin-film multilayered electrode or the like.
2 5 In the present invention, a pr~re.. td material constituting the adhesive layer is not limited to the aforementioned Ti. Other usable species of materials include Cr, Ni, and alloys co"l;.inillg at least one of them. For these m~teri~l~, the relations among the film thickntqss, the adhesion strength,and the resistivity show tendencies similar to the above-described tendencies of Ti.
-8- 2~84022 Ti, Cr, Ni, and other materials tend to combine with oxygen and result in increased resistivities. Therefore, films are preferably continuously formed in a vacuum. Specifically, a good thin-film multilayered electrode having a low resistivity can be mAmlfActured by continuously forming the adhesive layers, the conductive thin films in contact with the adhesive layers, and the dielectric thin films in a vacuum without breaking the vacuum during the process steps.
He~ arler, two embodiments of the present invention are explained in more detail with reference to the drawings.
0 Example 1 Fig. 4A is a perspective view showing a circular TM mode resondlor 10 comprising a dielectric substrate on which thin-film multilayered electrodes (a high frequency electrom~gnPtic field coupled type thin-film multilayered electrodes) according to one example of the invention are disposed.
In the circular TM mode resonator 10, a substAntiAlly circular R-surface sapphire substrate is used as the (li~1~ctric substrate 1. The thin-film multilayered electrodes 2 are disposed on both faces of the substMtes, respectively.
2 0 The thin-film multilayered electrodes 2 are formed by alternately st~cking thin-film conductors 7 and (lielectric thin films 4 of SiO2.
As shown in Fig. 4B, the thin-film conductor 7 includes a conductive film 3 con~icting essentially of Cu and a pair of adhesive layers 5 con~i~ting essentially of Ti or Cr and interposing the conductive film 3. Thus, as shown in Fig. SD, the adhesive layers 5 are disposed at the interface between the dielectric substMte 1 and the conductive thin film 3 and at the interface between the conductive thin film 3 and the dielectric thin film 4. Each pair of the thin-film conductors 7 and the dielectric thin film 4 sandwiched thel~belween con~titlltes a TEM mode trAnsmi~sic~n line, lhel~rol~, each of the 3 0 thin-film multilayered electrodes 2 includes a pluMlity of TEM mode trAn~mi~ion lines.
Based on a number of multilayered layers of the thin-film conductors 7 and the dielectric thin films 4, a film thickness of each of the dielectric thin films 4 is set so that phase velocities of TE~ waves which propagate through at least two of the plurality of TEM mode tr~n~mic~ion lines are made subst~nti~lly equal to each other. Moreover, based on the number of multilayered layers of the thin-film conductors 7 and the dielectric thin films 4, a film thickn~ss of each of the thin-film conductors 7 is set so as to be smaller than a skin depth of a frequency which is to be used so that electromagnetic fields of at least two of the plurality of TEM mode 0 1~n~mi~ciQn lines are coupled with each other.
A method of fabricating the aforementioned circular TM mode resonator is next described.
(1) As shown in Fig. SA, a metal mask 6 having a desired pattern is mounted on the dielectric substrate 1. The inside of a film formation chamber of ~ulle~ing equipment (not shown) is evAcll~te~l to a vacuum.
(2) Then, the adhesive layer 5 of Ti or Cr (Fig. SB) is formed on the dielectric substrate 1 by s~ulle~ g a target of Ti or Cr.
(3) Then, as shown in Fig. 5B, the first layer of conductive thin film 3 of Cu is formed on the adhesive layer 5 overlying the dielectric substrate 1 by ~ullelil g a target of Cu.
(4) Subsequently, the adhesive layer 5 (Fig. 5C) is formed on the conductive thin film 3a by sputt~ring a target of Ti or Cr.
(5) Then, as shown in Fig. 5C, the dielectric thin film 4 (thin film of SiO2) is formed on the adhesive layer 5 overlying the conductive thin film 3 by ~ulle -llg a target of SiO2.
Fig. 3 is a diagram showing the relation between the thickness of Ti thin films which can serve as adhesive layers and their resistivity.
Fig. 4A is a perspective view showing a circular TM mode resonator equipped with a thin-film multilayered electrode according to a first example of the invention.
Fig. 4B is a partial cross-sectional view of a thin-film conductor lo used in the circular TM mode resonator shown in Fig. 4A.
Figs. SA to SF are views illustrating a method of fabric~ting circular TM mode resonators equipped with thin-film multilayered electrodes according to the first example of the invention.
Fig. 6A is a perspective view of a microstrip line resonator equipped with a thin-film multilayered electrode according to a second example of the invention.
Fig. 6B is a partial cross-sectional view of a thin-film conductor used in the microstrip line resonator shown in Fig. 6A.
Figs. 7A to 7F are views illllstr~ting a method of fabricating 2 0 microstrip line resonators equipped with thin-film multilayered electrodes according to the second example of the invention.
The inventors of the present invention have conducted various experiments and studied abut methods of improving the strength with which the conductive thin films adhere to the dielectric substrate and to the dielectric thin films. It has been discovered that the strength is improved by placing an adhesive layer or layers of Ti or the like at the interface between the conductive thin film and the dielectric substrate or at the interfaces between the conductive thin films and the dielectric thin films.
That is, a thin-film multilayered electrode according to the 3 o present invention comprises a dielectric substrate on which conductive thin films and dielectric thin films are alternately multilayered. This thin-film 2~ 84022 multilayered electrode is characteri7ed in that an adhesive layer having a largeadhesion strength is placed at one or more of the interf~ces between the ~1ie1ectric substrate and the overlying conductive thin film and/or the interfaces between the conductive thin films and the dielectric thin films.
In the thin-film multilayered electrode according to the present invention, the adhesive layer having a large adhesion strength is a layer or thin film which provides larger adhesion strength when placed in the position of at least one of the above-mentioned interfaces, than if the conductive thin films were directly bonded to the dielectric substrate or to the dielectric thin1 o films.
It is preferable that the material of the adhesive layer or layers of the thin-film multilayered electrode be at least one species selected from the group con~i~ting of Ti, Cr, Ni, and alloys co~ inil-g at least one of them.
The adhesive layer has preferably a thickness of more than 20 nm.
A method of fabricating the thin-film multilayered electrode according to the invention is characterized in that the conductive thin films, the adhesive layer or layers, and the dielectric thin films are formed by continuous process steps under a vacuum without breaking the vacuum during the process steps.
2 o For example, where a thin Cu film having a film thickness of 1 ,um was formed as a conductive thin film on a glass substrate, or a dielectric substrate, a thin film of Ti was placed as an adhesive layer at the interface between the glass substrate and the Cu thin film. The relation of the film thickness of the Ti thin film and the adhesion strength obtained in this case isshown in Fig. 2. It can be seen from Fig. 2 that when the film thickness of the Ti thin film was less than about 20 nm, the adhesion strength was insufficient. In addition, a slight change in the film thickn~ ss resulted in a great variation of the adhesion strength. However, it was observed that as long as the thickness was more than about 20 nm, the adhesion strength was 3 0 sufficiently large. Furthermore, the stability was improved since the adhesion strength was subst~nti~11y constant.
A thin-film multilayered electrode was fabricated by alternately l~min~ting conductive thin films (Cu thin films) and dielectric thin films (glass thin films) on a dielectric substrate (glass substrate). An adhesive tape was stuck to the thin-film multilayered electrode and peeled off. Where thin films 5 of Ti having film thicknesses of less than 20 nm were placed at the interface between the dielectric substrate (glass substrate) and the conductive thin film (Cu thin film) and at the interfaces between the conductive thin films (Cu thin films) and the dielectric thin films (glass thin films), peeling of the multilayered films was observed. Where thin films of Ti having film thicknesses of more than 20 nm were placed, no peeling of the multilayered films was observed.
Thin films of Ti having various film thickn~sses were formed on glass substrates by ~u~e~-hlg techniques, and their resistivities were measured. The results are shown in Fig. 3. It can be seen from Fig. 3 that where the film thicknesses of the Ti thin films were less than about 20 nm, the electrical resistivities were rapidly increased and that a slight deviation from the design~l film thickness greatly affects the characteristics of the thin-film multilayered electrode with undesirable results. On the other hand, where the film thickn~sses of the Ti thin films were more than about 20 nm, 2 0 the resistivities were low. In addition, the stability was enhanced since the resistivity did not vary greatly with the thickness. Hence, a slight deviation from the design~d film thickness does not greatly affect the characteristics. Itcan be seen that this structure can be advantageously applied to an RF
electrom~gnt tic~lly coupled thin-film multilayered electrode or the like.
2 5 In the present invention, a pr~re.. td material constituting the adhesive layer is not limited to the aforementioned Ti. Other usable species of materials include Cr, Ni, and alloys co"l;.inillg at least one of them. For these m~teri~l~, the relations among the film thickntqss, the adhesion strength,and the resistivity show tendencies similar to the above-described tendencies of Ti.
-8- 2~84022 Ti, Cr, Ni, and other materials tend to combine with oxygen and result in increased resistivities. Therefore, films are preferably continuously formed in a vacuum. Specifically, a good thin-film multilayered electrode having a low resistivity can be mAmlfActured by continuously forming the adhesive layers, the conductive thin films in contact with the adhesive layers, and the dielectric thin films in a vacuum without breaking the vacuum during the process steps.
He~ arler, two embodiments of the present invention are explained in more detail with reference to the drawings.
0 Example 1 Fig. 4A is a perspective view showing a circular TM mode resondlor 10 comprising a dielectric substrate on which thin-film multilayered electrodes (a high frequency electrom~gnPtic field coupled type thin-film multilayered electrodes) according to one example of the invention are disposed.
In the circular TM mode resonator 10, a substAntiAlly circular R-surface sapphire substrate is used as the (li~1~ctric substrate 1. The thin-film multilayered electrodes 2 are disposed on both faces of the substMtes, respectively.
2 0 The thin-film multilayered electrodes 2 are formed by alternately st~cking thin-film conductors 7 and (lielectric thin films 4 of SiO2.
As shown in Fig. 4B, the thin-film conductor 7 includes a conductive film 3 con~icting essentially of Cu and a pair of adhesive layers 5 con~i~ting essentially of Ti or Cr and interposing the conductive film 3. Thus, as shown in Fig. SD, the adhesive layers 5 are disposed at the interface between the dielectric substMte 1 and the conductive thin film 3 and at the interface between the conductive thin film 3 and the dielectric thin film 4. Each pair of the thin-film conductors 7 and the dielectric thin film 4 sandwiched thel~belween con~titlltes a TEM mode trAnsmi~sic~n line, lhel~rol~, each of the 3 0 thin-film multilayered electrodes 2 includes a pluMlity of TEM mode trAn~mi~ion lines.
Based on a number of multilayered layers of the thin-film conductors 7 and the dielectric thin films 4, a film thickness of each of the dielectric thin films 4 is set so that phase velocities of TE~ waves which propagate through at least two of the plurality of TEM mode tr~n~mic~ion lines are made subst~nti~lly equal to each other. Moreover, based on the number of multilayered layers of the thin-film conductors 7 and the dielectric thin films 4, a film thickn~ss of each of the thin-film conductors 7 is set so as to be smaller than a skin depth of a frequency which is to be used so that electromagnetic fields of at least two of the plurality of TEM mode 0 1~n~mi~ciQn lines are coupled with each other.
A method of fabricating the aforementioned circular TM mode resonator is next described.
(1) As shown in Fig. SA, a metal mask 6 having a desired pattern is mounted on the dielectric substrate 1. The inside of a film formation chamber of ~ulle~ing equipment (not shown) is evAcll~te~l to a vacuum.
(2) Then, the adhesive layer 5 of Ti or Cr (Fig. SB) is formed on the dielectric substrate 1 by s~ulle~ g a target of Ti or Cr.
(3) Then, as shown in Fig. 5B, the first layer of conductive thin film 3 of Cu is formed on the adhesive layer 5 overlying the dielectric substrate 1 by ~ullelil g a target of Cu.
(4) Subsequently, the adhesive layer 5 (Fig. 5C) is formed on the conductive thin film 3a by sputt~ring a target of Ti or Cr.
(5) Then, as shown in Fig. 5C, the dielectric thin film 4 (thin film of SiO2) is formed on the adhesive layer 5 overlying the conductive thin film 3 by ~ulle -llg a target of SiO2.
(6) Then, the adhesive layer 5 is again formed on the dielectric thin film 4 by sputtering a target of Ti or Cr, as shown in Fig. 5D.
(7) Then, the above-explained operations (3)-(6) are repeated to 3 0 form each thin-film multilayered electrode 2 consisting of five layers of conductive thin films 3, as shown in Fig. 5E.
2 1 8 402~
(7) Then, the above-explained operations (3)-(6) are repeated to form each thin-film multilayered electrode 2 consisting of five layers of conductive thin films 3, as shown in Fig. SE.
2 1 8 402~
(7) Then, the above-explained operations (3)-(6) are repeated to form each thin-film multilayered electrode 2 consisting of five layers of conductive thin films 3, as shown in Fig. SE.
(8) Then, the film formation chamber is opened to the 5 atmosphere, and the operations (1)-(7) above are repeated. The thin-film multilayered electrode 2 is also formed on the other surface of the dielectric substrate 1, as shown in Fig. SF, thus fabricating the circular TM mode resonator shown in Fig. 4A.
The spulle~ g operations of the m~n~lf~cturing steps for 10 forming the adhesive layers, conductive thin films, and dielectric thin filmsof the above example are pelrol,lled under the conditions listed in Table 1.
Table 1 target Cu SiO2 Ti Cr s~ulleling gas Ar Ar/02 Ar Ar 15 gas flow rate (cc/min) gas pressure 1.0 X 10-3 1.4 x 10-3 9.0 X 10-3 9.0 X 10-3 background (torr) less than 1.0 x less than 1.0 x less than 1.0 x less than 1.0 x 10~ 10~ 10~ 10 substrate telllpelaLure (C) lS0 lS0 lS0 150 RF power (W) 600 600 600 600 As a comparative example, a circular TM mode resonator having no adhesive layer was fabricated by a process similar to the above-described method.
Table 2 shows the film thicknPsces of conductive thin films, 25 the film thicknesses of dielectric thin films, the presence or absence of adhesive layers, the kinds of the adhesive layers, the film thicknPsse~ of the adhesive layers, and the thicknesses of the dielectric sub~ tes of the circular TM mode resonators of the above example and of the comparative example having a resonance frequency of 3.0 Ghz.
- 11- 2l84o22 [Table 2 ]
sample 1 (co-l-rJaldlive 2 (example) 3 (example) example) thickness of conductive thin 0.525 O.S09 0.496 films (,um) thickn.o.ss of dielectric thin films0.401 0.450 0.440 (~m) presence or absence of adhesive layers absence presence presence o kind of adhesive - Ti Cr layers thickness of adhesive layers - 0.040 0.040 (~m) thickness of dielectric substrate 330 330 330 (~m) result of peelingpeeling occurred nopeeling no peeling test 2 o In order to examine the adhesion strengths of the thin-film multilayered electrodes of the circular TM mode resonators of the above examples and of the co,-,p~ ive example, peeling tests were performed.
That is, an adhesive tape was stuck to the thin-film multilayered electrodes 2 and peeled off. The results are also shown in Table 2. As shown in Table 2, peeling was observed in the thin-film multilayered electrode of the circular TM mode resonator of the colllpaldlive example where no adhesive layers were arranged. However, no peeling was observed at all in the thin-film multilayered electrodes of the circular TM mode resonators of the examples.
Example 2 Fig. 6A is a perspective view showing a microstrip line resonator 30 having a dielectric substrate on which thin-film multilayered electrodes according to another example of the invention are disposed.
This microstrip line resonator 30 has a dielectric substrate 21.
An R-surface sappl~ir~ substrate which is rectangular in its two-dimensional shape is used as the dielectric substrate 21. A thin-film multilayered electrode22 is disposed on the top surface. A ground electrode 27 is disposed on the bottom surface.
The thin-film multilayered electrode 22 is formed by alternately st~cking thin-film conductors 28 and ~ lectric thin films 24 of SiO2. As shown in Fig. 6B, the thin-film conductor 28 inchldes a conductive film 23 con~i~ting essentially of Cu and a pair of adhesive layers 25 con~i~ting essentially of Ti or Cr and interposing the conductive film 3. Thus, as shown in Fig. 7C, the adhesive layers 25 are disposed at the interface between the dielectric substrate 21 and the conductive thin film 23 and at the int~rf~ce between the conductive thin film 23 and the dielectric thin film 44. Each pair of the thin-film conductors 28 and the dielectric thin film 24 sandwiched tht;l~be~ween con~titutes a TEM mode tr~n~mi~ion line, therefore, the thin-2 o film multilayered electrodes 22 includes a plurality of TEM mode tf~n~mi~ion lines.
Based on a number of multilayered layers of the thin-film conductors 28 and the die1ectfic thin films 24, a film thicknPss of each of the dielectric thin films 24 is set so that phase velocities of TEM waves which propagate through at least two of the plurality of TEM mode tr~n~mi~ion lines are made subst~nti~11y equal to each other. Moreover, based on the number of multilayered layers of the thin-film conductors 28 and the dielectric thin films 24, a film thickness of each of the thin-film conductors 28 is set soas to be smaller than a skin depth of a frequency which is to be used so that 3 o electrom~gn~tic fields of at least two of the plurality of TEM mode tr~n~mi~ion lines are coupled with each other.
A method of fabric~tin~ the above-described microstrip line resonator is next described.
(1) The ~ lectric substrate 21 is put into the film formation chamber of s~uUel~g equipment (not shown). The inside is evacuated to a desired degree of vacuum. The adhesive layer 25 of Ti (Fig. 7A) is formed on the ~iielecttic substrate 21 by ~u~ g a target of Ti. Then, the first layer of conductive thin film 23 of Cu is formed on the adhesive layer 25 overlying the dielectric substrate 21 by sputtering a target of Cu, as shown in Fig. 7A.
(2) Subsequently, the adhesive layer 25 (Fig. 7B) is formed on the conductive thin film 23 by ~ulle~ g a target of Ti.
(3) Then, the dielectric thin film 24 (thin film of SiO2) is formed on the adhesive layer 25 overlying the conductive thin film 23 by ~ullelillg a target of SiO2, as shown in Fig. 7B.
(4) Then, the adhesive layer 25 (Fig. 7C) is formed on the dielectric thin film 24 by ~ullelUIg a target of Ti. Then, as shown in Fig.
7C, the conductive thin film 23 is formed on the adhesive layer 25 overlying the dielectric thin film 24.
(5) Then, the above-explained operations (2)-(4) are repeated to form a thin-film multilayered electrode 22a having the five conductive thin films 23, as shown in Fig. 7D. Thereafter, photoresist 26 is patterned and the thin-film multilayered electrode 22a is etched to form the thin-film multilayered electrode 22 as shown in Figs. 7D and 7E.
(6) Then, as shown in Fig. 7F, the grounding electrode 27 is formed on the bottom surface of the dielectric substrate 21, thus obtaining the microstrip line resonator as shown in Fig. 6A.
The conditions under which the ~ullering operations of the method of fabricating the thin-film multilayered electrode of this example 2 are the same as the conditions of the above-described example 1.
As a co-llpaldlive example, a microstrip line resonator having 3 o no adhesive layers was fabricated in a manner similar to the above-described method.
- 14- ~184022 Table 3 shows the film thicknesses of conductive thin films, the film thicknesses of ~ lectric thin films, the presence or absence of adhesive layers, the kinds of the adhesive layers, the film thicknesses of the adhesive layers, and the thicknPs~es of the dielectric substrates of the microstrip line 5 resonators of the above examples and of the colllpald~ive example having a resonance frequency of 2.0 Ghz.
[Table 3]
sample 4 (co,l,r~ ive 5 (example) example) thickness of conductive thin films 0.97 0.936 (~m) thickness of dielectric thin films 1.13 0.863 ~m) presence or absence of adhesive layers absence presence kind of adhesive layers - Ti thickn~ss of adhesive layers (,14m) - 0.040 thickn~ss of dielectric substrate 330 330 (llm) result of peeling test presence absence In order to examine the adhesion strengths of the thin-film 2 o multilayered electrodes of the microstrip line resonators of the above examples and of the co--~p~ ive example, peeling tests were performed. That is, an adhesive tape was stuck to the thin-flm multilayered electrodes 22 and peeled off. The results are also shown in Table 3. As shown in Table 3, peeling was observed in the thin-film multilayered electrode of the microstrip line resonator of the colllp~llive example where no adhesive layers were a~anged. However, no peeling was observed at all in the thin-film multilayered electrodes of the microstrip line resonators of the examples.
In the examples 1 and 2 above, the present invention of the subject application is applied to the thin-film multilayered electrodes of circular TM mode resonators and of microstrip line resonators. The thin-film multilayered electrode according to the invention and a method of fabri~ ~ting it are not limited to resonators. The invention can find wide application such as thin-film multilayered electrodes of other electronic parts and methods of fabricating them.
In the above examples l and 2, the adhesive layers are made of Ti or Cr. The material of the adhesive layers is not limited to these. Various materials such as Ni and alloys cont~ining at least one of Ti, Cr, and Ni can be used.
0 In the description of the above examples, the conductive thin films, the adhesive layers, and the dielectric thin films are formed by ~u~PIing. The method of forming the conductive thin films, the adhesive layers, and the dielectric thin films are not limited to the ~ulleling method.
Rather, various thin film formation methods such as vacuum evaporation, CVD, laser abrasion, and ion plating can be employed to form the thin films.
Also, in the description of the above examples, the adhesive layers are placed at all of the interfaces between the dielectric substrate and the conductive thin film formed on it, and the int.orf~ces between the conductive thin films and the dielectric thin films. Sometimes, the adhesive 2 o layers may not be required to be placed at every interface. The interfaces where the adhesive layers are placed can be determined according to the need.
In the description of the above examples l and 2, the five layers of conductive thin films alternate with the dielectric thin films. The number of the multilayered layers is not limited to this number. The number can be 2 5 made greater or smaller than the above-described number of multilayered layers.
With respect to other points, the present invention is not limited to the above examples. Various changes and mo-lific~tinns may be made to the dielectric material of the dielectric substrate, the kind of the conductive 3 o material of the conductive thin films, the thicknPsc of the adhesive layers, and so on within the scope of the spirit of the invention.
As described above, in the thin-film multilayered electrode according to the invention, an adhesive layer or layers of great adhesion strength are placed in the position of at least one of the interfaces between a dielectric substrate and a conductive thin film formed on it and/or the interfaces between conductive thin films and dielectric thin films. The strength of adhesion between the successive thin films forming the thin-f~
multilayered electrode is increased. This can enhance the reliability of the electrode.
Where the thin-film multilayered electrode according to the present invention is applied to an RF electrom~n~tically coupled thin-film multilayered electrode or the like used in a TM mode resonator or microstrip line resonator, it is assured that a reliable thin-film multilayered electrode can be obtained. This gives rise to an especially meaningful result.
In the thin-film multilayered electrode according to the present invention, at least one species selected from the group con~icting of Ti, Cr, Ni, and alloys co.l~;~inillg at least one of them is used as the m~t~ri~l of theadhesive layers. This assures that the adhesion strength can be ih~ oved.
Hence, the present invention can be made more effective.
Furthermore, by setting the thickn~ss of the adhesive layers to 2 o more than 20 nm, large and stable adhesion strength can be secured. This can make the present invention more effective.
Conductive thin f~s, adhesive layers, (li~lectric thin films are continuously formed in a vacuum without breaking the vacuum during the m~nuf~cturing steps. This assures that a thin-film multilayered electrode having a low resistivity is m~nnf~ct~lred while preventing the conductive thin films and the adhesive layers from oxidizing.
While p~elled embodiments of the invention have been disclosed, various modes of carrying out the principles disclosed herein are contemplated as being within the scope of the following claims. Therefore, it 3 o is understood that the scope of the invention is not to be limited except as otherwise set forth in the claims.
The spulle~ g operations of the m~n~lf~cturing steps for 10 forming the adhesive layers, conductive thin films, and dielectric thin filmsof the above example are pelrol,lled under the conditions listed in Table 1.
Table 1 target Cu SiO2 Ti Cr s~ulleling gas Ar Ar/02 Ar Ar 15 gas flow rate (cc/min) gas pressure 1.0 X 10-3 1.4 x 10-3 9.0 X 10-3 9.0 X 10-3 background (torr) less than 1.0 x less than 1.0 x less than 1.0 x less than 1.0 x 10~ 10~ 10~ 10 substrate telllpelaLure (C) lS0 lS0 lS0 150 RF power (W) 600 600 600 600 As a comparative example, a circular TM mode resonator having no adhesive layer was fabricated by a process similar to the above-described method.
Table 2 shows the film thicknPsces of conductive thin films, 25 the film thicknesses of dielectric thin films, the presence or absence of adhesive layers, the kinds of the adhesive layers, the film thicknPsse~ of the adhesive layers, and the thicknesses of the dielectric sub~ tes of the circular TM mode resonators of the above example and of the comparative example having a resonance frequency of 3.0 Ghz.
- 11- 2l84o22 [Table 2 ]
sample 1 (co-l-rJaldlive 2 (example) 3 (example) example) thickness of conductive thin 0.525 O.S09 0.496 films (,um) thickn.o.ss of dielectric thin films0.401 0.450 0.440 (~m) presence or absence of adhesive layers absence presence presence o kind of adhesive - Ti Cr layers thickness of adhesive layers - 0.040 0.040 (~m) thickness of dielectric substrate 330 330 330 (~m) result of peelingpeeling occurred nopeeling no peeling test 2 o In order to examine the adhesion strengths of the thin-film multilayered electrodes of the circular TM mode resonators of the above examples and of the co,-,p~ ive example, peeling tests were performed.
That is, an adhesive tape was stuck to the thin-film multilayered electrodes 2 and peeled off. The results are also shown in Table 2. As shown in Table 2, peeling was observed in the thin-film multilayered electrode of the circular TM mode resonator of the colllpaldlive example where no adhesive layers were arranged. However, no peeling was observed at all in the thin-film multilayered electrodes of the circular TM mode resonators of the examples.
Example 2 Fig. 6A is a perspective view showing a microstrip line resonator 30 having a dielectric substrate on which thin-film multilayered electrodes according to another example of the invention are disposed.
This microstrip line resonator 30 has a dielectric substrate 21.
An R-surface sappl~ir~ substrate which is rectangular in its two-dimensional shape is used as the dielectric substrate 21. A thin-film multilayered electrode22 is disposed on the top surface. A ground electrode 27 is disposed on the bottom surface.
The thin-film multilayered electrode 22 is formed by alternately st~cking thin-film conductors 28 and ~ lectric thin films 24 of SiO2. As shown in Fig. 6B, the thin-film conductor 28 inchldes a conductive film 23 con~i~ting essentially of Cu and a pair of adhesive layers 25 con~i~ting essentially of Ti or Cr and interposing the conductive film 3. Thus, as shown in Fig. 7C, the adhesive layers 25 are disposed at the interface between the dielectric substrate 21 and the conductive thin film 23 and at the int~rf~ce between the conductive thin film 23 and the dielectric thin film 44. Each pair of the thin-film conductors 28 and the dielectric thin film 24 sandwiched tht;l~be~ween con~titutes a TEM mode tr~n~mi~ion line, therefore, the thin-2 o film multilayered electrodes 22 includes a plurality of TEM mode tf~n~mi~ion lines.
Based on a number of multilayered layers of the thin-film conductors 28 and the die1ectfic thin films 24, a film thicknPss of each of the dielectric thin films 24 is set so that phase velocities of TEM waves which propagate through at least two of the plurality of TEM mode tr~n~mi~ion lines are made subst~nti~11y equal to each other. Moreover, based on the number of multilayered layers of the thin-film conductors 28 and the dielectric thin films 24, a film thickness of each of the thin-film conductors 28 is set soas to be smaller than a skin depth of a frequency which is to be used so that 3 o electrom~gn~tic fields of at least two of the plurality of TEM mode tr~n~mi~ion lines are coupled with each other.
A method of fabric~tin~ the above-described microstrip line resonator is next described.
(1) The ~ lectric substrate 21 is put into the film formation chamber of s~uUel~g equipment (not shown). The inside is evacuated to a desired degree of vacuum. The adhesive layer 25 of Ti (Fig. 7A) is formed on the ~iielecttic substrate 21 by ~u~ g a target of Ti. Then, the first layer of conductive thin film 23 of Cu is formed on the adhesive layer 25 overlying the dielectric substrate 21 by sputtering a target of Cu, as shown in Fig. 7A.
(2) Subsequently, the adhesive layer 25 (Fig. 7B) is formed on the conductive thin film 23 by ~ulle~ g a target of Ti.
(3) Then, the dielectric thin film 24 (thin film of SiO2) is formed on the adhesive layer 25 overlying the conductive thin film 23 by ~ullelillg a target of SiO2, as shown in Fig. 7B.
(4) Then, the adhesive layer 25 (Fig. 7C) is formed on the dielectric thin film 24 by ~ullelUIg a target of Ti. Then, as shown in Fig.
7C, the conductive thin film 23 is formed on the adhesive layer 25 overlying the dielectric thin film 24.
(5) Then, the above-explained operations (2)-(4) are repeated to form a thin-film multilayered electrode 22a having the five conductive thin films 23, as shown in Fig. 7D. Thereafter, photoresist 26 is patterned and the thin-film multilayered electrode 22a is etched to form the thin-film multilayered electrode 22 as shown in Figs. 7D and 7E.
(6) Then, as shown in Fig. 7F, the grounding electrode 27 is formed on the bottom surface of the dielectric substrate 21, thus obtaining the microstrip line resonator as shown in Fig. 6A.
The conditions under which the ~ullering operations of the method of fabricating the thin-film multilayered electrode of this example 2 are the same as the conditions of the above-described example 1.
As a co-llpaldlive example, a microstrip line resonator having 3 o no adhesive layers was fabricated in a manner similar to the above-described method.
- 14- ~184022 Table 3 shows the film thicknesses of conductive thin films, the film thicknesses of ~ lectric thin films, the presence or absence of adhesive layers, the kinds of the adhesive layers, the film thicknesses of the adhesive layers, and the thicknPs~es of the dielectric substrates of the microstrip line 5 resonators of the above examples and of the colllpald~ive example having a resonance frequency of 2.0 Ghz.
[Table 3]
sample 4 (co,l,r~ ive 5 (example) example) thickness of conductive thin films 0.97 0.936 (~m) thickness of dielectric thin films 1.13 0.863 ~m) presence or absence of adhesive layers absence presence kind of adhesive layers - Ti thickn~ss of adhesive layers (,14m) - 0.040 thickn~ss of dielectric substrate 330 330 (llm) result of peeling test presence absence In order to examine the adhesion strengths of the thin-film 2 o multilayered electrodes of the microstrip line resonators of the above examples and of the co--~p~ ive example, peeling tests were performed. That is, an adhesive tape was stuck to the thin-flm multilayered electrodes 22 and peeled off. The results are also shown in Table 3. As shown in Table 3, peeling was observed in the thin-film multilayered electrode of the microstrip line resonator of the colllp~llive example where no adhesive layers were a~anged. However, no peeling was observed at all in the thin-film multilayered electrodes of the microstrip line resonators of the examples.
In the examples 1 and 2 above, the present invention of the subject application is applied to the thin-film multilayered electrodes of circular TM mode resonators and of microstrip line resonators. The thin-film multilayered electrode according to the invention and a method of fabri~ ~ting it are not limited to resonators. The invention can find wide application such as thin-film multilayered electrodes of other electronic parts and methods of fabricating them.
In the above examples l and 2, the adhesive layers are made of Ti or Cr. The material of the adhesive layers is not limited to these. Various materials such as Ni and alloys cont~ining at least one of Ti, Cr, and Ni can be used.
0 In the description of the above examples, the conductive thin films, the adhesive layers, and the dielectric thin films are formed by ~u~PIing. The method of forming the conductive thin films, the adhesive layers, and the dielectric thin films are not limited to the ~ulleling method.
Rather, various thin film formation methods such as vacuum evaporation, CVD, laser abrasion, and ion plating can be employed to form the thin films.
Also, in the description of the above examples, the adhesive layers are placed at all of the interfaces between the dielectric substrate and the conductive thin film formed on it, and the int.orf~ces between the conductive thin films and the dielectric thin films. Sometimes, the adhesive 2 o layers may not be required to be placed at every interface. The interfaces where the adhesive layers are placed can be determined according to the need.
In the description of the above examples l and 2, the five layers of conductive thin films alternate with the dielectric thin films. The number of the multilayered layers is not limited to this number. The number can be 2 5 made greater or smaller than the above-described number of multilayered layers.
With respect to other points, the present invention is not limited to the above examples. Various changes and mo-lific~tinns may be made to the dielectric material of the dielectric substrate, the kind of the conductive 3 o material of the conductive thin films, the thicknPsc of the adhesive layers, and so on within the scope of the spirit of the invention.
As described above, in the thin-film multilayered electrode according to the invention, an adhesive layer or layers of great adhesion strength are placed in the position of at least one of the interfaces between a dielectric substrate and a conductive thin film formed on it and/or the interfaces between conductive thin films and dielectric thin films. The strength of adhesion between the successive thin films forming the thin-f~
multilayered electrode is increased. This can enhance the reliability of the electrode.
Where the thin-film multilayered electrode according to the present invention is applied to an RF electrom~n~tically coupled thin-film multilayered electrode or the like used in a TM mode resonator or microstrip line resonator, it is assured that a reliable thin-film multilayered electrode can be obtained. This gives rise to an especially meaningful result.
In the thin-film multilayered electrode according to the present invention, at least one species selected from the group con~icting of Ti, Cr, Ni, and alloys co.l~;~inillg at least one of them is used as the m~t~ri~l of theadhesive layers. This assures that the adhesion strength can be ih~ oved.
Hence, the present invention can be made more effective.
Furthermore, by setting the thickn~ss of the adhesive layers to 2 o more than 20 nm, large and stable adhesion strength can be secured. This can make the present invention more effective.
Conductive thin f~s, adhesive layers, (li~lectric thin films are continuously formed in a vacuum without breaking the vacuum during the m~nuf~cturing steps. This assures that a thin-film multilayered electrode having a low resistivity is m~nnf~ct~lred while preventing the conductive thin films and the adhesive layers from oxidizing.
While p~elled embodiments of the invention have been disclosed, various modes of carrying out the principles disclosed herein are contemplated as being within the scope of the following claims. Therefore, it 3 o is understood that the scope of the invention is not to be limited except as otherwise set forth in the claims.
Claims (6)
1. A thin-film multilayered electrode of a high frequency electromagnetic field coupled type, comprising:
a plurality of thin-film conductors and dielectric thin films alternately stacked on a dielectric substrate so as to form a plurality of TEM mode transmission lines, each pair of thin-film conductors and the dielectric thin film sandwiched therebetween constituting a TEM mode transmission line;
wherein each of the dielectric thin films has a predetermined film thickness based on a number of layers of the thin-film conductors and the dielectric thin films, so that phase velocities of TEM waves which propagate through at least two of the plurality of TEM mode transmission lines are made substantially equal to each other;
wherein each of the thin-film conductors has a predetermined film thickness based on the number of layers of the thin-film conductors and the dielectric thin films, such that said predetermined film thickness is smaller than a skin depth of a predetermined frequency which is to be used, so that electromagnetic fields of at least two of the plurality of TEM mode transmission lines are coupled with each other;
wherein at least one of the thin-film conductors further includes at least one adhesive layer having a large adhesion strength at one or more of the interfaces between the dielectric substrate and the thin-film conductor and the interfaces between the thin film conductors and the dielectric thin films; and wherein the adhesive layer is made of at least one kind of material selected from the group consisting of Ti, Cr, Ni, and alloys containing at least one of them.
a plurality of thin-film conductors and dielectric thin films alternately stacked on a dielectric substrate so as to form a plurality of TEM mode transmission lines, each pair of thin-film conductors and the dielectric thin film sandwiched therebetween constituting a TEM mode transmission line;
wherein each of the dielectric thin films has a predetermined film thickness based on a number of layers of the thin-film conductors and the dielectric thin films, so that phase velocities of TEM waves which propagate through at least two of the plurality of TEM mode transmission lines are made substantially equal to each other;
wherein each of the thin-film conductors has a predetermined film thickness based on the number of layers of the thin-film conductors and the dielectric thin films, such that said predetermined film thickness is smaller than a skin depth of a predetermined frequency which is to be used, so that electromagnetic fields of at least two of the plurality of TEM mode transmission lines are coupled with each other;
wherein at least one of the thin-film conductors further includes at least one adhesive layer having a large adhesion strength at one or more of the interfaces between the dielectric substrate and the thin-film conductor and the interfaces between the thin film conductors and the dielectric thin films; and wherein the adhesive layer is made of at least one kind of material selected from the group consisting of Ti, Cr, Ni, and alloys containing at least one of them.
2. The thin-film multilayered electrode according to claim 1, wherein the adhesive layer has a thickness of more than about 20 nm.
3. A thin-film multilayered electrode of a high frequency electromagnetic field coupled type, comprising:
a plurality of thin-film conductors and dielectric thin films alternately stacked on a dielectric substrate so as to form a plurality of TEM mode transmission lines, each pair of thin-film conductors and the dielectric thin film sandwiched therebetween constituting a TEM mode transmission line;
wherein each of the dielectric thin films has a predetermined film thickness based on a number of layers of the thin-film conductors and the dielectric thin films, so that phase velocities of TEM waves which propagate through at least two of the plurality of TEM mode transmission lines are made substantially equal to each other;
wherein each of the thin-film conductors has a predetermined film thickness based on the number of layers of the thin-film conductors and the dielectric thin films, such that said predetermined film thickness is smaller than a skin depth of a predetermined frequency which is to be used, so that electromagnetic fields of at least two of the plurality of TEM mode transmission lines are coupled with each other;
wherein at least one cf the thin-film conductors further includes at least one adhesive layer having a large adhesion strength at one or more of the interfaces between the dielectric substrate and the thin-film conductor and the interfaces between the thin film conductors and the dielectric thin films: and wherein the adhesive lager has a thickness of more than about 20 nm.
a plurality of thin-film conductors and dielectric thin films alternately stacked on a dielectric substrate so as to form a plurality of TEM mode transmission lines, each pair of thin-film conductors and the dielectric thin film sandwiched therebetween constituting a TEM mode transmission line;
wherein each of the dielectric thin films has a predetermined film thickness based on a number of layers of the thin-film conductors and the dielectric thin films, so that phase velocities of TEM waves which propagate through at least two of the plurality of TEM mode transmission lines are made substantially equal to each other;
wherein each of the thin-film conductors has a predetermined film thickness based on the number of layers of the thin-film conductors and the dielectric thin films, such that said predetermined film thickness is smaller than a skin depth of a predetermined frequency which is to be used, so that electromagnetic fields of at least two of the plurality of TEM mode transmission lines are coupled with each other;
wherein at least one cf the thin-film conductors further includes at least one adhesive layer having a large adhesion strength at one or more of the interfaces between the dielectric substrate and the thin-film conductor and the interfaces between the thin film conductors and the dielectric thin films: and wherein the adhesive lager has a thickness of more than about 20 nm.
4. A thin-film multilayered electrode of a high frequency electromagnetic field coupled type, comprising:
a plurality of thin-film conductors and dielectric thin films alternately stacked on a dielectric substrate so as to form a plurality of TEM mode transmission lines, each pair of thin-film conductors and the dielectric thin film sandwiched therebetween constituting a TEM mode transmission line;
wherein at least one of the thin-film conductors further includes at least one adhesive layer having a large adhesion strength at one or more of the interfaces between the dielectric substrate and the thin-film conductor and the interfaces between the thin film conductors and the dielectric thin films; and wherein the adhesive layer is made of at least one kind of material selected from the group consisting of Ti, Cr, Ni, and alloys containing at least one of them.
a plurality of thin-film conductors and dielectric thin films alternately stacked on a dielectric substrate so as to form a plurality of TEM mode transmission lines, each pair of thin-film conductors and the dielectric thin film sandwiched therebetween constituting a TEM mode transmission line;
wherein at least one of the thin-film conductors further includes at least one adhesive layer having a large adhesion strength at one or more of the interfaces between the dielectric substrate and the thin-film conductor and the interfaces between the thin film conductors and the dielectric thin films; and wherein the adhesive layer is made of at least one kind of material selected from the group consisting of Ti, Cr, Ni, and alloys containing at least one of them.
5. The thin-film multilayered electrode according to claim 4, wherein the adhesive layer has a thickness of more than about 20 nm.
6. A thin-film multilayered electrode of a high frequency electromagnetic field coupled type, comprising:
a plurality of thin-film conductors and dielectric thin films alternately stacked on a dielectric substrate so as to form a plurality of TEM mode transmission lines, each pair of thin-film conductors and the dielectric thin film sandwiched therebetween constituting a TEM mode transmission line;
wherein at least one of the thin-film conductors further includes at least one adhesive layer having a large adhesion strength at one or more of the interfaces between the dielectric substrate and the thin-film conductor and the interfaces between the thin film conductors and the dielectric thin films; and wherein the adhesive layer has a thickness of more than about 20 nm.
a plurality of thin-film conductors and dielectric thin films alternately stacked on a dielectric substrate so as to form a plurality of TEM mode transmission lines, each pair of thin-film conductors and the dielectric thin film sandwiched therebetween constituting a TEM mode transmission line;
wherein at least one of the thin-film conductors further includes at least one adhesive layer having a large adhesion strength at one or more of the interfaces between the dielectric substrate and the thin-film conductor and the interfaces between the thin film conductors and the dielectric thin films; and wherein the adhesive layer has a thickness of more than about 20 nm.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7-239125 | 1995-08-23 | ||
| JP7239125A JPH0964609A (en) | 1995-08-23 | 1995-08-23 | Thin film laminated electrode and its production |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2184022A1 CA2184022A1 (en) | 1997-02-24 |
| CA2184022C true CA2184022C (en) | 1999-11-02 |
Family
ID=17040164
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002184022A Expired - Fee Related CA2184022C (en) | 1995-08-23 | 1996-08-23 | Thin-film multilayered electrodes and method of fabricating same |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US5770988A (en) |
| EP (1) | EP0759642B1 (en) |
| JP (1) | JPH0964609A (en) |
| KR (1) | KR100217462B1 (en) |
| CA (1) | CA2184022C (en) |
| DE (1) | DE69629882T2 (en) |
| TW (1) | TW301810B (en) |
Families Citing this family (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3087651B2 (en) * | 1996-06-03 | 2000-09-11 | 株式会社村田製作所 | Thin film multilayer electrode, high frequency transmission line, high frequency resonator and high frequency filter |
| EP0957530B1 (en) * | 1997-01-28 | 2006-02-22 | Murata Manufacturing Co., Ltd. | Dielectric resonator, dielectric filter, dielectric duplexer, and method for manufacturing dielectric resonator |
| JPH11177310A (en) * | 1997-10-09 | 1999-07-02 | Murata Mfg Co Ltd | High frequency transmission line, dielectric resonator, filter, duplexer and communication equipment |
| DE69831549T2 (en) * | 1997-10-21 | 2006-06-14 | Murata Manufacturing Co | Thin film multilayer electrode, high frequency transmission line, high frequency resonator and high frequency filter |
| US6238812B1 (en) | 1998-04-06 | 2001-05-29 | Paul M. Brown | Isotopic semiconductor batteries |
| US6118204A (en) * | 1999-02-01 | 2000-09-12 | Brown; Paul M. | Layered metal foil semiconductor power device |
| JP4754670B2 (en) * | 1999-11-05 | 2011-08-24 | 住友大阪セメント株式会社 | Optical waveguide device |
| GB0012437D0 (en) * | 2000-05-24 | 2000-07-12 | Univ Cranfield | Improvements to filters |
| US7026886B2 (en) * | 2003-10-09 | 2006-04-11 | National Chiao Tung University | Miniaturized microwave integrated circuit using complementary conducting surfaces |
| US20080272857A1 (en) * | 2007-05-03 | 2008-11-06 | Honeywell International Inc. | Tunable millimeter-wave mems phase-shifter |
| JP2009181623A (en) * | 2008-01-30 | 2009-08-13 | Fujitsu Ltd | Magnetic head and manufacturing method thereof |
| US9728304B2 (en) | 2009-07-16 | 2017-08-08 | Pct International, Inc. | Shielding tape with multiple foil layers |
| CN103259069B (en) * | 2013-04-12 | 2015-06-24 | 上海安费诺永亿通讯电子有限公司 | Transmission line capable of reducing loss |
| CN103259070B (en) * | 2013-04-12 | 2016-08-03 | 上海安费诺永亿通讯电子有限公司 | The low-loss transmission line of a kind of fall |
| US11626228B2 (en) * | 2016-12-22 | 2023-04-11 | Rogers Corporation | Multi-layer magneto-dielectric material |
| CN106992120A (en) * | 2017-04-10 | 2017-07-28 | 华南理工大学 | One kind display highly conductive coupling electrode of electronic device and preparation method thereof |
| CN108963402B (en) * | 2018-08-16 | 2023-09-26 | 北京华镁钛科技有限公司 | Transmission structure for manufacturing radio frequency microwave device and antenna and manufacturing method |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2769148A (en) * | 1951-03-07 | 1956-10-30 | Bell Telephone Labor Inc | Electrical conductors |
| US2879183A (en) * | 1955-12-15 | 1959-03-24 | Bell Telephone Labor Inc | Insulating coatings and a method for their production |
| US4157518A (en) * | 1977-07-27 | 1979-06-05 | Belden Corporation | Leaky coaxial cable having shield layer with uniform gap |
| US5355105A (en) * | 1993-04-12 | 1994-10-11 | Angelucci Sr Thomas L | Multi-layer flexible printed circuit and method of making same |
| JP3089666B2 (en) * | 1993-08-27 | 2000-09-18 | 株式会社村田製作所 | High frequency transmission line, high frequency resonator, high frequency filter and high frequency band elimination filter |
-
1995
- 1995-08-23 JP JP7239125A patent/JPH0964609A/en active Pending
-
1996
- 1996-08-21 TW TW085110183A patent/TW301810B/zh active
- 1996-08-22 US US08/701,384 patent/US5770988A/en not_active Expired - Fee Related
- 1996-08-23 EP EP96113571A patent/EP0759642B1/en not_active Expired - Lifetime
- 1996-08-23 DE DE69629882T patent/DE69629882T2/en not_active Expired - Fee Related
- 1996-08-23 CA CA002184022A patent/CA2184022C/en not_active Expired - Fee Related
- 1996-08-23 KR KR1019960035132A patent/KR100217462B1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| EP0759642B1 (en) | 2003-09-10 |
| US5770988A (en) | 1998-06-23 |
| JPH0964609A (en) | 1997-03-07 |
| DE69629882T2 (en) | 2004-07-29 |
| DE69629882D1 (en) | 2003-10-16 |
| KR100217462B1 (en) | 1999-09-01 |
| CA2184022A1 (en) | 1997-02-24 |
| TW301810B (en) | 1997-04-01 |
| EP0759642A1 (en) | 1997-02-26 |
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